Fantasy, sci-fi, romance are all fine for me. However, give me a period piece, Western, or God forbid, a war story and I'm out of my element. As an English major, I've read many period pieces. The research doesn't bother me, but setting the tone and getting the details right would drive me to distraction. Westerns, again, due to a lack experience. You can create a flying dragon and explain how it feels, yet no one can clock you as having the details wrong. Write about riding a horse, the tack, and how it feels after a day in the saddle, and people everywhere will tell if you get a detail wrong because they live it. Finally, war stories make me uncomfortable. I have difficulty seeing, add in a weapon that must be aimed and I'm doomed. Now add moving targets and bullets aimed at me, well, to be honest, I'm completely lost. I haven't been a soldier, and it feels wrong to ask one what it is like to kill, barely survive, and live with the aftermath to get it right for a story. Almost anything else I can research and create, but those, well I just can't seem to strike the right tone when attempting to write them, so, I stay away from them.